Pickup feed mechanism for phonographs



Aug. 29, 1944. L. THOMPSON I PICKUP FEED MECHANISM FOR'PHONOGRAPHS Filed May 28, 1945 INVENTOR Ll/vc'auv THUMPSO/V ATTORNEY L. THOMPSON 2,357,033-

PICKUP FEED MECHANISM FOR PHONOGRAPHS Filed May 28, 1943' 2 Sheets-Shet 2 IN V EN TOR. J. in coin 'Zh ompson BY machines, and more Patented Aug. 29, 1944 PICKUP FEED MECHANISM FOR PHONOGRAPHS Lincoln Thompson, Cheshire, Conn., assignor to The S oundscriber Corporation,

New Haven,

Conn., a corporation of Connecticut Application May 28, 1943, Serial No. 488,829

8 Claims.

This invention relates to dictating phonograph particularly to a feed mechanism for positively crossed cable.

A further object is to provide a dictating machine of the above nature, in which the cable is I connected with a friction-slipping take-up lo-' cated inside the pickup arm pulley, whereby the;

pickup arm may be adjusted manually to any desired position. l

A further object is to provide a dictating machine of the above nature which will be simple in construction, inexpensive to manufacture, easy to install and manipulate, ornamental in appearance, and very eflicient and durable in use.

With these and other objects in view there has be 11 illustrated upon the accompanying drawsame, taken 1, looking in the same showing the record and turntable located beneath the'pickup head.

This invention is an improvement over themof the pickup arm showvention disclosed in my prior Patent No. 2,316,637 entitled Phonograph record scanning devices, of April 13, 1943.

The invention is particularly adapted for operation in connection with a dictating machine of the type disclosed in my Reissue Patent No. 22,183 of September'22, 19.42, entitled Apparatus for recording sounds on thin disks; in my Patent No. 2,133,596 of October'18, 1938, entitled Feed mechanism for disk recording machines; in my Patent No. 2,213,936 of September 3, 1940, entitled Electrodynamic pickup, and in my Patent No. 2,250,242 of July 22, 1941, entiled Disk dictating machines.

In the reproduction of disk sound records having closely-spaced relatively shallow embossed of the record, the record out of thus causing skips or repeats during'the transcription. A discontinuous groove clue to an interruption in the recording may also cause the pickup needle to skip or repeat. 5

By means of the present invention the above and other disadvantages have been avoided and mechanism has been provided which will positively maintain the pickup stylus within the recorded groove.

In a dictating machine of this type a diamondtipped stylus is generally employed in the re- The sound is recorded by means of the lateral vibrations of the stylus which produce lateral undulations in the groove.

In playing back or transcribing the record, a sapphire-tipped reproducing stylus is generally employed. This stylus is adapted to fit in the the pickup head. i

In the present invention the feed mechanism for the pickup arm a spring take-up to maintain a constant friction on the shaft pulleys. friction is determined by the smoothness. of the pulley surfaces and by their diameter, as well as should be so adjusted as to permitirelatively easy movement or the reproducing pickup arm to 2 facilitate handling, and to produce tight enough control so that accidental shocks will not move the pickup arm from the normal position as held there by the friction. The feed on the reproducing stylus should follow exactly the feed produced on the record by the recording stylus; therefore, the pulleys must be of the same diameter, and the radius of rotation of the reproducing stylus must be equal to the radius of rotation of the recording stylus when the record was made. Furthermore, the two arms must be symmetrically placed so that when swung past the center of the record, their styli must be equal amounts ahead or behind the center, or pass exactly through the center, whichever position Y is the most desirable one.

As herein illustrated, the well known principle of bending the end portions of the recording and reproducing arms is employed so as to provide for a substantially tangential contact between the styli and the record grooves in the usable portion thereof. This has the obvious advantage of giving better sound recording and reproduction. It also serves to eliminate the effect of any lateral forces, due to frictional contact, which would tend to move the stylus out of its groove.

Referring now to the drawings in which like reference numerals denote corresponding parts throughout the several views, the numeral l indicates the base of a dictating machine, which is provided with a horizontal turntable mounted to rotate above said base, and which is adapted to be driven by means of a vertical spindle |2, which in turn is driven by a suitable motor, not shown.

Mounted upon the turntable for rotation therewith 'is a thin disk record tablet |3, preferably made in accordance with the specifications of the above mentioned Reissue Patent No. 22,183. g

Sound grooves are adapted to be engraved or embossed in the record tablet |3, by means of an electrically-actuated recording head 30, carrying a recording stylus, notshown, and adapted to be swung in an arc over the turntable H, by

means of an angular recording arm l4, frictionally' secured'upon a vertical feed shaft [6, which saidarm |4 loosely surrounds. Below the base III, the shaft f6 has rigidly secured thereto a worm gear l1 which meshes with a worm I8 driven by a motor or other source of power, not shown.'

The worm gear and the worm l8 are adapted to be enclosed by a protective casing T9 secured to the underside of the base l0, and said casing is provided at its center with a seat |9a for a bearing disk20 which is adapted to engage a hub |'|b of said worm gear I1. Below the bearing disk 2|], provision is made. of a washer 2| which is pressed against said disk by a coiled spring 22, the lower end of which is seated'upon a second washer 23, which in turn is supported byan adjustable nut 24 located upon the lower end of the shaft I6.

Provision is also made of a power head 24a, connected by a pin |Ba tothe shaft l6 and having a slip-friction engagement with the under surface of a rear hub 24b of'the recording arm |'4.

By means of this construction it will be seen that by, varying the pressure ofv the spring 22, and adjusting the nut 24, the "amount of friction between the bearing disk 20 and the hub |'|b may be controlled. i

It will be understood thatby "driving the rethe record and in cording arm through the slip-friction power head 24a, backlash will be entirely avoided.

The sound vibrations recorded in the embossed spiral grooves of the record l3 are adapted to be reproduced or transcribed by means of a sapphire-tipped stylus carried by the reproducing or pickup head 3| mounted upon the pickup arm l5. 3

In order to transmit power from the recording arm shaft IE to the pickup arm 15 for swinging the pickup arm l5 at constant speed across the opposite direction from the motion of the recording arm [4, provision is made of a pair of hollow metal pulleys 25 and 35 mounted upon the upper ends of the shafts l6 and 32, respectively, said pulleys being yieldably connected together by means of a metal cable 31, preferably made of phosphor bronze, and known in the trade as radio dial cable, as will be hereinafter fully described.

The pulley 25 is provided with a central upstanding collar 26, upon which a nut 21 is seated, said nut being screwed upon the upper end of the feed shaft l6. Below the pulley 25, provision is made of a spring 28 which presses downwardly upon the rear end of the recording arm l4 and upwardly upon a washer 29, which in turn engages the under surface of said pulley 25.

The shaft 32 of the reproducing arm I5 is relatively short and is mountedto rotate between 'a pair of cone-bearings 33 and 34 which are .carried by a U-shaped bracket '43 attached by a headed screw 44 to the base ll! of the dictating machine.

The pulley 35 is provided with a cutaway sector, on one side of which is an inwardly extending vertical flange 39 to which one end 38 of the cable 31 is secured, said pulley-35 being secured to the pickup arm 15 in any suitable manner, as by a pair of screws 36 and 36a, adjustably located in a pair of arcuate slots 36b and 36c in a horizontal inturned lip 42 of said pulley 35. a

The cable 31 makes two turns around the pulley 25, as clearly shown in 'Fig. 2, to provide a non-slipping connection therewith, and the free end 40 of said cable is secured to an adjustable coiled take-up spring 4|, which in turn is secured to the screw 36a on the pulley 35.

The recording head 30 is embraced by a raised yoke plate 45 integral with the recording arm I4, and is mounted, preferably at its center of gravity, upon a pair of horizontal pivot screws 46 secured to a pair of legs depending from said yoke plate. A pair" of heads, 41 and 48, are provided on the ends of the'pivot screws 46, and a constant lifting force will be exerted upon the rear of the recording head 30 by means of a light coil tension spring secured to a bracket member 53 passing through an aperture 55 in the yoke plate 45. The recording stylus will thus be pressed with a constant force upon the record. The mounting of the recording head is similar to that disclosed in my prior application, Serial No. 463,791, filed October29, 1942', entitled Stylus head mountings for dictatingmachines.

The. pickup head 3| is embraced by a raised yoke plate 49, similar tothe "yoke plate 45, and said head 3| is mounted, preferably at its center of gravity on'a pair of vertical cone pivots 51, 58 in a small tubular carriage '50. which is pivoted on a pair of horizontal pointed pins 5| and 52 mounted in a pair of legs 59, 60 depending from the yoke plate 49. By means of this mounting on both vertical and horizontal pivots, the pickup head will be permitted to move about in each direction. The pickup head 3| is pressed against the record with a constant pressure by means of a lifting coiled spring member 54 passing through an aperture 56, which spring member being secured at its lower end to a pin El on the pickup head 3| and at its upper end to a bracket 53a mounted on the rear of the yoke plate 49.

It is well known that in all disk records there is a certain amount of eccentricity, and this is particularly the case with thin plastic records. The action of heat alone will often render a record oval-shaped by the amount of several grooves; therefore, the reproducing stylus when connected to a feed mechanism must have a certain amount of play in order to take care of the eccentricity. The tension coil spring 54 located at the back of the pickup head serves the combined function of forcing the pickup needle against the record and yieldably maintaining the pickup head in its normal centralized position.

It will be understood that the recorder feed shaft l6 and its pulley are driven constantly, so that the pickup feed cable 31 will also be in constant motion, even though the recording arm Will normally be locked against movement while the record is being reproduced by the pickup.

One advantage of the present invention is that the dictating machine is completely stabilized as far as its resistance to shock is concerned, and that in conjunction with the mounting of the stylus heads at their centers of gravity it is actually possible to reproduce a record when tilted at various angles and even when the machine is upside down.

While there has been disclosed in this specification one form in which the invention may be embodied, it is to be understood that this form is shown for the purpose of illustration only and that the invention is not to be limited to the specific disclosure but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming Within the scope of the following claims.

Having thus fully described the invention, what is claimed as new and for which it is desired to secure Letters Patent, is:

1. In a sound reproducing machine, a rotatable disk record, a constantly driven feed shaft having a recording arm mounted thereon, a pickup arm pivotally mounted to swing over said record, a shaft rigidly secured to said pickuparm, each of said shafts having a pulley mounted thereon, and a cable passing around both of said pulleys for driving said pickup arm from said feed shaft.

2. In a sound reproducing machine, a rotatable disk record, a constantly driven feed shaft having a recording arm mounted thereon, a pickup arm pivotally mounted to swing over said record, a shaft rigidly secured to said pickup arm, each of said shafts having a pulley mounted on the upper end thereof, and a cable passing around both of said pulleys for driving said pickup arm from said feed shaft.

3. In a sound recording and reproducing ma- 3 chine, a rotatabl disk record, a recording arm pivotally mounted to swing over said record, a constantly driven feed shaft yieldably connected to said recording arm for driving said arm across said'record, a pickup arm also pivotally mounted to swing over said to said pickup arm, each of said shafts having a I pulley mounted thereon, and a crossed cable passing around said pulleys for driving said pickup arm from said feed shaft.

4. In a dictating machine, a rotatable turntable having a center spindle, a disk record mounted thereon, a recording arm pivotally mounted to swing over said record, a recording head carried by said arm, a constantly driven feed shaft connected to said recording arm for swinging the latter across, said record, a pickup carrying arm also pivotally mounted to swing across said record, said pickup head lying on the opposite side of said spindle as said recording head, means operatively connecting said feed shaft with said pickup arm whereby said pickup head will be positively fed across the record during reproduction at the same speed as the recording head during recording.

5. The invention as defined in Claim 1, in which said pickup arm has its free end inclined inwardly into substantial tangency with the usable portion of the record grooves.

6. In a sound recording and reproducing machine, a rotatable disk record, a constantly driven feed shaft having a recording arm mounted thereon, a pickup arm pivotally mounted to swing over said record, a shaft rigidly secured to said pickup arm, each of said shafts having a pulley mounted thereon, and a cable passing around both of said pulleys for driving said pickup arm from said feed shaft, one end of said cable being rigidly secured to said pickup arm pulley, and the other end of said cable being resiliently secured to said pickup arm pulley.

7. In a sound reproducing machine, a rotatable disk record, a constantly driven feed shaft having said pulleys for driving said pickup arm from said feed shaft, one end of said cable being cured to said pickup 8.- In a sound reproducing-machine, a rotatable disk record, a constantly driven feed shaft having a recording arm mounted thereon, a pickup arm pivotally mounted to swing over said record, a pivot shaft rigidly secured to said pickup arm, each of said shafts having a pulley mounted thereon, a slip fraction cable passing around said pulleys for driving said pickup arm from said feed shaft, one end of said cable being rigidly secured to said pickup arm pulley, and .a coiled take-up spring secured to the other end of said cable and also securedto said pickup arm pulley.

LINCOLN THOMPSON.

record, a shaft rigidly secured 

